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C. Shieh, I. C. Han, G. J. Jaffe; Evaluation of Signal Strength and Spectral Domain OCT Image Artifacts. Invest. Ophthalmol. Vis. Sci. 2009;50(13):1083.
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© ARVO (1962-2015); The Authors (2016-present)
Signal strength is a parameter that combines signal to noise ratio (SNR) and the uniformity of the signal within an OCT scan. Many clinicians use signal strength to decide on the quality and utility of the OCT images. In this retrospective observational case series, we determined whether signal strength impacts the frequency and type of OCT artifacts.
Records from patients who underwent an ophthalmologic evaluation by a member of the Duke University Eye Center vitreoretinal faculty (GJJ) and had a spectral domain OCT scan (Cirrus) produced between August 2007 and November 2007 were reviewed. The relationship between OCT scan artifacts and signal strength was determined for scans with signal strength of 4 or above, using the Spearman rank correlation.
Scans from 104 eyes were analyzed. Retinal scan algorithm errors and scan artifacts were identified in 85.53% of all eyes. Of these, the four most common -- inner retinal misidentification (75%), outer retinal misidentification (60.57%), out of register (36.53%) and degraded image artifact (33.65%) were identified in 84.61 % of all eyes. Other artifacts were also identified but were not included due to the small proportion.The Spearman’s rank correlation of signal strength and inner retinal misidentification was [[Unsupported Character - Codename ­]]0.36 (p<0.001). For outer retinal misidentification, r= -0.06 (p=0.528); for degraded, r = -0.41 (<0 .001), and for out of register, r =0.04 (p=0.70). The Spearman’s rank correlation of signal strength and all four artifacts was -0.30 (p=0.002).
Cirrus spectral domain artifacts occurred frequently, and were minimally to moderately associated inversely with signal strength. However, artifacts were seen in scans with high signal strength, and relatively artifact-free scans were observed with low signal strength. Signal strength is not an optimal method to assess OCT scan quality.
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